No hissing serpent!

(Thomas Boston, "Human Nature in its Fourfold State")

Believers shall be made completely happy in the kingdom of Heaven. They shall be fully freed from sin, which of all evils, is the worst.

They shall be free from all temptation to sin. Satan can have no access to tempt them any more, by himself, or by his agents. No hissing serpent can come into the paradise above! No snare or trap can be laid there, to catch the feet of the saints. They may walk there without fear, for they can be in no hazard in the promised land. They shall be set beyond the possibility of sinning, for they shall be confirmed in holiness.

The guilt and the reigning power of sin are then taken away. The corrupt nature will be fully removed, and no vestiges of it left in their souls. Their nature shall be altogether pure and sinless.

There shall be no darkness in their minds; but the understanding will be as a globe of pure and unmixed light.

There shall not be the least aversion to good, nor the least inclination to evil, in their wills. They will be brought to a perfect conformity to the will of God — blessed with angelic purity, and fixed therein.

Their affections shall not be liable to the least disorder or irregularity. They will get such a fixed habit of purity, as they can never lose. They will be so refined from all earthly dross, as never more to savor of anything but of Heaven.

Their graces shall then be fully perfected.
There will be no more ground for complaints . . .
  of weakness of grace,
  or of an evil heart,
  or a corrupt nature.

And they shall be freed from all the effects of sin: "God will remove all of their sorrows, and there will be no more death or sorrow or crying or pain. For the old world and its evils are gone forever!" Revelation 21:4

In Heaven they find the completion and satisfaction of all their desires — having the full enjoyment of God, and uninterrupted communion with Him. In the heavenly Canaan, Immanuel's land — nothing is lacking to complete the happiness of the inhabitants. This is the holy and happy country — blessed with a perpetual spring, and which yields all things for necessity, convenience, and delight!